Abstract
Carcinogenic effect of radiation is known to depend on age of exposure. In mouse liver, irradiation at 0-7 days of age is reported to be most effective. In an attempt to understand the molecular mechanisms underlying the phenomena, we analyzed the alteration of gene expression at mRNA levels. Mice were exposed to 3.8 Gy whole body irradiation at 7 days of age or 10 weeks of age. Another group was sham-irradiated. Each group was divided further into two; fed normal-diet or caloric-restricted (CR) diet. At 10 months of age, we compared the gene expression levels in the liver of all 5 groups to that of control group (sham-irradiated, fed normal-diet). Microarray and quantitative RT-PCR analysis revealed that the expression of the 3 genes was altered in the liver irradiated at 7 days of age; two genes showed increased expression and one showed decreased expression. Expression levels of the 3 genes in the liver irradiated at 10 weeks of age were similar to those irradiated at 7 days of age. This suggested the change in expression levels of the 3 genes was not related to carcinogenic events. The CR effect on 3.8 Gy irradiated mice was complicated. The study could not find alteration of mRNA which would explain age-dependency of radiation induced liver cancer. But we found 3 genes whose expression levels were altered long time after irradiation in mouse liver.
